<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 17. Debug Mode</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="C++, library, debug" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="extensions.html" title="Part III.  Extensions" /><link rel="prev" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks" /><link rel="next" href="debug_mode_semantics.html" title="Semantics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 17. Debug Mode</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><th width="60%" align="center">Part III. 
  Extensions
  
</th><td width="20%" align="right"> <a accesskey="n" href="debug_mode_semantics.html">Next</a></td></tr></table><hr /></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.debug_mode"></a>Chapter 17. Debug Mode</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="debug_mode.html#manual.ext.debug_mode.intro">Intro</a></span></dt><dt><span class="section"><a href="debug_mode_semantics.html">Semantics</a></span></dt><dt><span class="section"><a href="debug_mode_using.html">Using</a></span></dt><dd><dl><dt><span class="section"><a href="debug_mode_using.html#debug_mode.using.mode">Using the Debug Mode</a></span></dt><dt><span class="section"><a href="debug_mode_using.html#debug_mode.using.specific">Using a Specific Debug Container</a></span></dt></dl></dd><dt><span class="section"><a href="debug_mode_design.html">Design</a></span></dt><dd><dl><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.goals">Goals</a></span></dt><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods">Methods</a></span></dt><dd><dl><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods.wrappers">The Wrapper Model</a></span></dt><dd><dl><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods.safe_iter">Safe Iterators</a></span></dt><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods.safe_seq">Safe Sequences (Containers)</a></span></dt></dl></dd><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods.precond">Precondition Checking</a></span></dt><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.methods.coexistence">Release- and debug-mode coexistence</a></span></dt><dd><dl><dt><span class="section"><a href="debug_mode_design.html#methods.coexistence.compile">Compile-time coexistence of release- and debug-mode components</a></span></dt><dt><span class="section"><a href="debug_mode_design.html#methods.coexistence.link">Link- and run-time coexistence of release- and
    debug-mode components</a></span></dt><dt><span class="section"><a href="debug_mode_design.html#methods.coexistence.alt">Alternatives for Coexistence</a></span></dt></dl></dd></dl></dd><dt><span class="section"><a href="debug_mode_design.html#debug_mode.design.other">Other Implementations</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.intro"></a>Intro</h2></div></div></div><p>
    By default, libstdc++ is built with efficiency in mind, and
    therefore performs little or no error checking that is not
    required by the C++ standard. This means that programs that
    incorrectly use the C++ standard library will exhibit behavior
    that is not portable and may not even be predictable, because they
    tread into implementation-specific or undefined behavior. To
    detect some of these errors before they can become problematic,
    libstdc++ offers a debug mode that provides additional checking of
    library facilities, and will report errors in the use of libstdc++
    as soon as they can be detected by emitting a description of the
    problem to standard error and aborting the program.  This debug
    mode is available with GCC 3.4.0 and later versions.
  </p><p>
    The libstdc++ debug mode performs checking for many areas of the
    C++ standard, but the focus is on checking interactions among
    standard iterators, containers, and algorithms, including:
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="emphasis"><em>Safe iterators</em></span>: Iterators keep track of the
    container whose elements they reference, so errors such as
    incrementing a past-the-end iterator or dereferencing an iterator
    that points to a container that has been destructed are diagnosed
    immediately.</p></li><li class="listitem"><p><span class="emphasis"><em>Algorithm preconditions</em></span>: Algorithms attempt to
    validate their input parameters to detect errors as early as
    possible. For instance, the <code class="code">set_intersection</code>
    algorithm requires that its iterator
    parameters <code class="code">first1</code> and <code class="code">last1</code> form a valid
    iterator range, and that the sequence
    [<code class="code">first1</code>, <code class="code">last1</code>) is sorted according to
    the same predicate that was passed
    to <code class="code">set_intersection</code>; the libstdc++ debug mode will
    detect an error if the sequence is not sorted or was sorted by a
    different predicate.</p></li></ul></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="debug_mode_semantics.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 16. Compile Time Checks </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Semantics</td></tr></table></div></body></html>